Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations
Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations
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DOI：
10.1038/s41586-020-2177-0
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发表时间：
2020-04-16
期刊：
影响因子：
64.8
通讯作者：
Zykova, A.
中科院分区：
文献类型：
--
作者：
Abe, K.;Akutsu, R.;Zykova, A.
基本粒子的电荷共轭和宇称反转（CP）对称是物质和反物质之间的对称。CP对称性的破坏在1964年首次被观察到（1），夸克弱相互作用中的CP破坏很快被确定（2）。萨哈罗夫提出（3）CP破坏对于解释宇宙中物质和反物质丰度的不平衡是必要的。然而，夸克中的CP破坏太小，无法支持这种解释。到目前为止，在非夸克基本粒子系统中还没有观察到CP破坏。已经证明，轻子中的CP破坏可以通过一个称为轻子生成的过程产生物质-反物质不一致性（4）。轻子混合，出现在标准模型的带电电流相互作用（5，6），提供了一个潜在的来源CP破坏通过一个复杂的相位dCP，这是所需要的一些理论模型的leptogenesis（7-9）。这种CP破坏可以在μ中微子到电子中微子振荡和相应的反中微子振荡中测量，这可以通过使用加速器产生的光束进行实验，如Tokai-to-Kamioka（T2 K）和NOvA实验（10，11）所建立的。到目前为止，dCP的值还没有受到中微子振荡实验的实质性限制。在这里，我们报告的测量使用长基线中微子和反中微子振荡所观察到的T2 K实验，表明中微子振荡概率大幅增加，不包括dCP值，导致在三个标准偏差（3西格玛）的反中微子振荡概率大幅增加。delta（CP）的3 sigma置信区间是循环的，每2 p重复一次，对于所谓的正常质量排序是[-3.41，-0.03]，对于反向质量排序是[-2.54，-0.32]。我们的研究结果表明，CP破坏轻子和我们的方法，使敏感的中微子振荡的物质反物质不对称性的搜索使用加速器产生的中微子束。未来更大数据集的测量将测试轻子CP破坏是否大于夸克中的CP破坏。
The charge-conjugation and parity-reversal (CP) symmetry of fundamental particles is a symmetry between matter and antimatter. Violation of this CP symmetry was first observed in 1964(1), and CP violation in the weak interactions of quarks was soon established(2). Sakharov proposed(3) that CP violation is necessary to explain the observed imbalance of matter and antimatter abundance in the Universe. However, CP violation in quarks is too small to support this explanation. So far, CP violation has not been observed in non-quark elementary particle systems. It has been shown that CP violation in leptons could generate the matter-antimatter disparity through a process called leptogenesis(4). Leptonic mixing, which appears in the standard model's charged current interactions(5,6), provides a potential source of CP violation through a complex phase dCP, which is required by some theoretical models of leptogenesis(7-9). This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible using accelerator-produced beams as established by the Tokai-to-Kamioka (T2K) and NOvA experiments(10,11). Until now, the value of dCP has not been substantially constrained by neutrino oscillation experiments. Here we report a measurement using long-baseline neutrino and antineutrino oscillations observed by the T2K experiment that shows a large increase in the neutrino oscillation probability, excluding values of dCP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3 sigma). The 3 sigma confidence interval for delta(CP), which is cyclic and repeats every 2p, is [-3.41, -0.03] for the so-called normal mass ordering and [-2.54, -0.32] for the inverted mass ordering. Our results indicate CP violation in leptons and our method enables sensitive searches for matter-antimatter asymmetry in neutrino oscillations using accelerator-produced neutrino beams. Future measurements with larger datasets will test whether leptonic CP violation is larger than the CP violation in quarks.